Louisville (usually pronounced ; see Pronunciation]] below) is Kentucky's largest [[city. It is ranked as either the 17th or 27th largest city in the United States depending on how the population is calculated (see Nomenclature, population, and ranking below). The settlement that became the City of Louisville was founded in 1778 by George Rogers Clark and is named after King Louis XVI of France. Louisville is famous as the home of "The Most Exciting Two Minutes in Sports": the Kentucky Derby, the widely watched first race of the Triple Crown of Thoroughbred Racing.

Louisville is situated in north-central Kentucky on the Kentucky-Indiana border at the only natural obstacle in the Ohio River, the Falls of the Ohio. Louisville is the county seat of Jefferson County, and since 2003, the city's borders are coterminous with those of the county due to merger. Because it includes counties in Southern Indiana, the Louisville metropolitan area is regularly referred to as Kentuckiana. A resident of Louisville is referred to as a Louisvillian. Although situated in a Southern state, Louisville is influenced by both Midwestern and Southern culture, and is commonly referred to as either the northernmost Southern city or the southernmost Northern city in the United States.

Louisville has been the site of many important innovations through history. Notable residents have included inventor Thomas Edison, US Supreme Court Justice Louis Brandeis, boxing legend Muhammad Ali, newscaster Diane Sawyer, actor Tom Cruise, and writers Hunter S. Thompson and Sue Grafton. Notable events occurring in the city include the first public viewing place of Edison's light bulb, the first library open to African Americans in the South, and medical advances including the first human hand transplant, the first self-contained artificial heart transplant, and the development site of the first cervical cancer vaccine.

As of the 2000 Census, Louisville had a population of 256,231; which for the first time since 1820 was less than the population of Lexington, a city with a consolidated city-county government. However, on November 7, 2000 voters in Louisville and Jefferson County approved their own ballot measure to merge into a consolidated city-county government named Louisville-Jefferson County Metro Government (official long form) and Louisville Metro (official short form), which took effect January 1, 2003. The Jefferson County-Louisville merger has a population more than twice as large as Lexington-Fayette.

The U.S. Census Bureau gives two different population figures for Louisville: for the consolidated Louisville-Jefferson County it lists the 2006 estimated population as 701,500 (17th largest in the nation and equal to that of Jefferson County);Census Population Estimates for 2006 (line 25213) for the Louisville-Jefferson County balance it lists the population as 554,496 (27th largest).Census Population Estimates for 2006 - Annual Estimates of the Population for Incorporated Places Over 100,000 (line 31) The "balance" is a designation created by the Census Bureau to describe the portion of Louisville-Jefferson County that does not include any of the semi-independent separately incorporated places located within Louisville Metro (such as Anchorage, Middletown or Jeffersontown).For what geographic areas does the Census Bureau produce estimates?